1. Field of the Invention
The invention relates to a running control apparatus for a vehicle. More specifically, the invention relates to a running control apparatus that controls the running movement of a vehicle by controlling the steering angle of a steering wheel and the braking/driving force for the wheel.
2. Description of the Related Art
Japanese Patent Application Publication No. JP-A-2003-175749 describes an example of a running control apparatus for a vehicle such as an automobile. The running control apparatus includes steering means, braking/driving force control means, calculation means, division means, and control means. The steering means steers a steering wheel, independently of steering operation performed by a driver. The braking/driving force control means controls the braking/driving force for each wheel. The calculation means calculates a target turning control amount, such as a target yaw moment of the vehicle. The division means divides the target turning control amount into a target turning control amount allocated to the control of the steering angle of the steering wheel and a target turning control amount allocated to the control of the braking/driving force in predetermined proportions. The control means controls the steering means based on the target turning control amount allocated to the control of the steering angle of the steering wheel, and controls the braking/driving force control means based on the target turning control amount allocated to the control of the braking/driving force.
In general, the running movement of the vehicle can be controlled by steering the steering wheel using the steering means, without accelerating or decelerating the vehicle. However, the vehicle moves in slower response to driver's driving operation than when the running movement is controlled by controlling the braking/driving force. Also, it is difficult to deal with understeer of the vehicle. In contrast, when the running movement of the vehicle is controlled by controlling the braking/driving force, the vehicle moves in quicker response to the driver's driving operation than when the running movement is controlled by steering the steering wheel. However, the vehicle speed needs to be changed, that is, the vehicle needs to be accelerated or decelerated.
With the aforementioned running control apparatus, the target turning control amount is divided into the target turning control amount allocated to the control of the steering angle of the steering wheel and the target turning control amount allocated to the control of the braking/driving force, in the predetermined proportions. The proportions are set based on, for example, the responsiveness and characteristics of the steering means and the braking/driving force control means. Therefore, as compared to the case where the running movement of the vehicle is controlled only by controlling the steering angle of the steering wheel or only by controlling the braking/driving force, the running movement of the vehicle can be appropriately and effectively controlled.
However, in the aforementioned running control apparatus, the proportions are set based on, for example, the responsiveness and characteristics of the steering means and the braking/driving force control means (responsiveness and characteristics for obtaining the target turning control amount), without taking into account the running mode desired by an occupant or the intention of a driver. Therefore, the target turning control amount cannot be appropriately allocated to the steering means and to the braking/driving force control means according to the running mode desired by the occupant and the intention of the driver.